Water is the best known corrosive agent causing rapid corrosion, either directly or indirectly, of most types of metallic surfaces, especially those of iron or iron alloys such as steel. Therefore, protection or resistance against corrosion from water and water-soluble corrosive reactants has been a primary concern of research and development, concomitant with the universal utilization of metallic, particularly, iron containing materials.
Both molybdate and carboxylate compounds are known in the art to act as rust and other corrosion preventatives. These carboxylates are typically salts of mono-, di-, or tribasic alkyl or aryl acids. Gluconates, for example, have been well recognized as masking or sequestering compounds tending to form organic complexes with iron and aluminum in near neutral solutions as well as with calcium in alkaline media. Thus, sodium gluconate, zinc gluconate, blends of alkali metal gluconate and sodium gluconate have been found useful as corrosion inhibitors of mild steel.
It has been proposed that carboxylates such as gluconate inhibit steel corrosion by forming a protective, i.e., hydrophobic layer in the form of insoluble iron carboxylate complexes whereby an Fe.sup.3+ state is maintained by dissolved oxygen. Indeed, numerous carboxylate compounds are described in the literature on cooling water, metal working fluids, or antifreeze, etc. as being inhibitors of ferrous metal corrosion.
We have made the surprising discovery that the present novel organomolybdenum compounds exhibit unexpected efficacy as corrosion inhibitors compared to conventional agents in immersion or gravimetric and electrochemical tests. Moreover, the novel compounds have exhibited advantageous physical and chemical properties such as high stability in concentrated storage solutions and good resistance to sunlight and heat effects.